1. Field of Utility Model
The present invention relates to a sheetfed scanning apparatus, and more particularly to a structure for mounting a transparent plate and a color reference slice in the sheetfed scanning apparatus.
2. Related Art
The scanning apparatus in a sheetfed scanner or multi-functional-printer (MFP) has a transparent plate made of transparent materials such as glass, and paper sheets moving on the transparent plate are scanned by a scanning module, so as to produce and then output the image data. The transparent plate is mainly used for separating the paper sheets from the scanning module, so as to prevent the paper sheets from contacting the scanning module directly, and to form a smooth plane pervious to light. Thus the paper sheets pass over scanning module evenly, and thereby accurate image data are captured by the scanning module.
Moreover, during scanning, a color reference is required for a control circuit of the scanning apparatus to correct the color and color level of the captured image, such that the captured image data shows the accurate color and color level of the original image. In general, a color reference slice is disposed in the scanning apparatus as a color reference, such that when scanning the paper sheets, the scanning module also captures the image of the color reference slice, and then corrects the image data with the color and color level of the color reference slice as a correction reference.
Referring to FIG. 1, it shows a sheetfed scanning apparatus 100 in the prior art. The sheetfed scanning apparatus 100 includes a cover 110 and a base 120, and a spacing distance exists there-between to form a paper-feeding track 130 for paper sheets to pass therethrough. A scanning window 121 is opened on the base 120, and a transparent plate 140 is firmly fixed at the scanning window 121 by a clamping plate 123 which is fixed by a screw 122 on lower side of the base 120. The transparent plate 140 is clamped and fixed on the lower side of the base 120 where the scanning window 121 is covered thereby. A scanning module 150 is disposed below the base 120 corresponding to the scanning window 121 to scan the paper sheet passing over the transparent plate 140. A color reference slice 160 is disposed at the cover 110 corresponding to the scanning window 121 to provide color reference for the scanning module 150. However, with this method, if the assembly tolerance is relatively large, the spacing distance between the color reference slice 160 and the plane through which the paper sheet passes is changed, and thereby the optical condition is changed, so that the color reference slice 160 for each scanning apparatus 100 shows different color references, resulting in different scanning results for different scanning apparatuses 100.
Referring to FIG. 2, it shows another sheetfed scanning apparatus 200 in the prior art. When fixing a transparent plate 240, a color reference slice 260 is clamped below the transparent plate 240 by a clamping plate 223, such that the distance between the plane through which the paper sheet passes while being scanned and the color reference slice 260 is always equal to the thickness of the transparent plate 240. As long as the thickness tolerance of the transparent plate 240 falls within a predetermined range, the color reference values produced by the color reference slices 260 of different scanning apparatuses 200 tend to be the same. However, the paper sheet and the color reference slice 260 are separated on two sides of the transparent plate 240 in this design, such that the color reference value actually captured by the scanning module 250 is still influenced by the transparent plate 240, and thereby the optical condition of the paper sheet cannot be truly presented, resulting in differences in the scanning results.
Moreover, in the aforementioned designs of FIGS. 1 and 2, the plane through which paper sheet actually passes is different from the plane where the color reference slice 160 or 260 is located, such that the difference between the optical condition of the paper sheet and that of the color reference slice cannot be actually presented. Therefore, repeated tests are required for processing the color reference value of the scanning module 150, 250 obtained by the color reference slice 160, 260 respectively to obtain a modification parameter, which truly acts as the color reference value when the paper sheet is scanned. Also, additional elements are required for fixing the color reference slice and the transparent plate, thus, the assembly is quite inconvenient.